It is known to provide vehicles with a transmission, also known as a gearbox, for providing speed and torque conversions between a rotating power source, engine or motor. For example between a crankshaft of an internal combustion engine and a driveshaft coupled to one or more differentials which drive the road wheels.
A typical manual transmission comprises an input shaft and an output shaft. The input shaft is coupled to the crankshaft of an engine via a clutch and flywheel.
The output shaft is coupled to the drive wheels via a drive shaft and one or more differentials or additional gears.
The input shaft comprises a plurality of gears, normally helical gears, which are fixed to the input shaft. The output shaft comprises a plurality of gears, one for each of the gears on the input shaft, the gears on the output shaft are “floating” that is to say they are mounted on bearings so as to rotate freely about the output shaft.
The output shaft also comprises a plurality of activators fixedly mounted thereon, which rotate with the output shaft.
The activators comprise a locking mechanism for locking with a floating gear, typically a dog clutch.
It is known to combine a cone clutch with a dog clutch to create a synchroniser; the cone clutch engages first, in a frictional engagement with the selected gear to match the speed of the floating gear with the output shaft; once the speed is matched the activator is moved into locking engagement with the gear by engaging the dog clutch.
The activator may comprise a cone clutch and dog clutch on both sides for engagement with different gears.
The process of selecting or activating an individual gear comprises an initial friction stage that helps to synchronise gear and shaft speed. In this stage a sleeve provided on the activator pushes against a ring that blocks its way and this applies force to the friction interface.
When the speed is synchronous the blocking ring is pushed out of the way and the sleeve is free to continue its travel towards the gear. Once the blocking ring is moved, the synchroniser will not be able to generate any more friction unless the activator is returned to a neutral position and the process started again. If the initial speeds of the gear and shaft are synchronous, the friction phase will not be activated. After the friction phase is completed and the sleeve has travelled up to the locking interface of the gear, the locking phase takes place with the sleeve locking the gear to the shaft using the dog clutch. When returning the activator back to the neutral position the friction phase cannot be activated again and the only task performed is release of the gear, there is no control of torque or speed during the release stage.
The present invention seeks to overcome or at least mitigate the problems of the prior art.